This invention relates to an operator-movable, single lever control lever assembly with friction-held, detent-held and spring-centered operational modes.
It is well-known to use manual control levers to remotely control hydraulic functions, such as hydraulic motors or cylinders. For example, friction-held control levers are used to remotely control implement hitches on agricultural vehicles wherein the control lever is moved to a friction-held displaced position to cause the hitch to raise or lower to a new position corresponding to the displaced control lever position. A friction-held control lever is also used to control the rotation speed of hydraulic motors where the rotation speed is maintained at a value corresponding to the control lever position. Spring-centered and detent-held control levers are used to control hydraulic functions through a selective control valve, as described in U.S. Pat. No. 3,721,160. In such an application, the control lever is moved to a detent-held displaced position to hydraulically extend or retract a hydraulic cylinder. When the actuated hydraulic cylinder reaches the end of its stroke, the detent is automatically released by a pressure signal and the lever returns to its neutral position under the influence of a centering spring, whereupon the cylinder is held in the extended or retracted position. Single levers with both friction-held and spring-centered operational modes are disclosed in U.S. patent applications, Ser. No. 307,704, filed Oct. 2, 1981 and Ser. No. 333,601, (attorney's file no. E-12050), filed Dec. 23, 1981, both assigned to the assignee of the present application. Although functional, both designs were subject to certain shortcomings. For example, in the first design, the mode-selecting solenoid is pivotal with the movable lever, thus subjecting the connecting electrical wires to wear from repeated flexing. Also, that design was energy-inefficient because the mode-selecting solenoid had to be constantly energized during its spring-centered operational mode. Furthermore, in that design, the friction force provided by the friction disks was somewhat less than desirable. Also, in the first design, separate actuators are required to operate the detent and centering spring mechanisms. In the second design, the centering spring is never uncoupled, thus requiring that the friction mechanism provides friction sufficient to overcome the centering spring during the friction-held operational mode. Furthermore, the second design required multiple energizations of the mode-selecting solenoid to switch between the friction and spring-centered operational modes. Accordingly, it would be desirable to provide a compact, multiple mode, single lever control lever assembly with adequate durability, improved energy utilization and with a centering spring which may be de-coupled.